This invention relates generally to ultrasonic diagnostic systems that use ultrasonic transducers to produce ultrasonic echoes from the interior of the body, and more particularly, to ultrasonic diagnostic systems that use scanheads having an integral beamformer and a demountable transducer array.
Ultrasonic diagnostic imaging systems are in widespread use for performing ultrasonic imaging and measurements. For example, cardiologists, radiologists, and obstetricians use ultrasonic imaging systems to examine the heart, various abdominal organs, or a developing fetus, respectively. Diagnostic images are obtained from these systems by placing a scanhead against the skin of a patient, and actuating an ultrasonic transducer located within the scanhead to transmit ultrasonic energy through the skin and into the body of the patient. In response, ultrasonic echoes are reflected from the interior structure of the body, and the returning acoustic echoes are converted into electrical signals by the transducer in the scanhead.
FIG. 1 shows an ultrasonic imaging system 10 according to the prior art. A scanhead assembly 11 includes a handle portion 18 that supports a transducer assembly 16. The transducer assembly 16 is generally formed from a crystalline material, such as barium titanate or lead zirconate titanate (PZT), that is shaped to form a number of piezoelectric elements 17 capable of transmitting and receiving signals at ultrasonic frequencies. The piezoelectric elements 17 thus formed may be arranged in a linear array, or alternatively, they may be arranged in a variety of two-dimensional configurations. A scanhead cable 20 is coupled to the scanhead assembly 11 at one end, and to an ultrasonic processor 12 at the opposing end to permit the processor 12 and the scanhead assembly 11 to communicate. The ultrasonic processor 12 contains a beamformer 22 capable of exchanging signals with the scanhead assembly 11 to dynamically focus the ultrasonic signals emitted by the transducer assembly 16. Dynamic focus is achieved by controlling the relative time delays of the applied voltages on each element so that they are combined to produce a net ultrasonic signal focused at a selected point within the body being scanned. The focal point thus achieved can be moved on each successive transmitter excitation, so that the transmitted signals can be scanned across the body at various depths within the body without moving the transducer. Similar principles apply when the transducer receives a return echo from an interior region of the body. The voltages produced at the transducer elements 17 are individually delayed in time and then summed so that the net signal is dominated by the acoustic echoes reflected from a single receive focal point in the body. The dynamically focused signals may then be transferred to an image processor 24 located within the processor 12 for subsequent additional processing prior to displaying a visual image of the scanned region of the body on a visual display 14. A system controller 26 cooperatively interacts with the beamformer 22 and the image processor 24 to control the processing of the beamformed signals and the data flow from the beamformer 22.
The need for more detailed diagnostic information from ultrasound systems has progressively led to the development of systems with transducer assemblies that contain a large number of individual piezoelectric elements 17. As a result, the transducer assembly 16 may contain individual piezoelectric elements in numbers that range from a few hundred elements to as many as three thousand. Generally, each element 17 of the transducer assembly 16 must be coupled to the processor 12 by an individual coaxial line. Since all of the coaxial lines extend through the scanhead cable 20, the diameter of the scanhead cable 20 increases as the number of array elements 17 increases. Consequently, as transducer assemblies increase in size, the scanhead cable 20 becomes increasingly more difficult to manipulate during ultrasonic procedures due to decreased cable flexibility. Further, as the size and complexity of transducer arrays steadily increases, the diameter and weight of the scanhead cable 20 may become prohibitively large at some point.
In an effort to reduce the number of coaxial lines in the scanhead cable 20, prior art ultrasonic imaging systems have employed multiplexers positioned within the scanhead assembly 11 to selectively transmit and receive ultrasonic signals from the elements 17 of the transducer assembly 16. Since multiplexing permits a coaxial line to communicate with more than a single transducer element 17, the overall size of the scanhead cable 20 is reduced. Although this approach has allowed fewer coaxial lines to be used with larger array sizes, multiplexing adversely affects the aperture size, and hence the resolution of the ultrasonic imaging device since it limits the number of elements 17 that may be simultaneously active. Multiplexing may also adversely affect the frame rate of the ultrasonic imaging device.
Other prior art methods have transferred at least a portion of the signal processing from the processor 12 to the scanhead assembly 11, thus reducing the number of individual coaxial lines in the scanhead cable 20. For example, U.S. Pat. No. 6,102,863 to Pflugrath, et al. describes an ultrasonic imaging system where at least some of the beamforming processing has been moved from the processor 12 to the scanhead assembly 11. Although this approach allows an overall reduction in the number of coaxial lines in the scanhead cable, significant shortcomings still exist. For example, when it is desired to use a different transducer assembly for a particular diagnostic procedure, the scanhead assembly and the beamforming processor must both be changed since the transducer assembly is permanently coupled to the beamforming processor. Further, in the event that the transducer assembly either wholly or partially fails, the relatively costly beamforming processor might have to be discarded along with the failed transducer assembly.
Therefore, there is a critical need for a scanhead that can be coupled to an ultrasonic processor through a relatively thin cable despite having a large number of elements, and that can be replaced relatively inexpensively in the event that one or more elements fail.
The present invention is directed to a scanhead having an integral beamformer and a transducer assembly that is demountable from the scanhead. The scanhead has a frontal portion including a transducer assembly, and a rear portion including a beamformer. The frontal portion further includes a connective interface to electrically communicate with a corresponding connective interface on the rear portion. In one aspect of the invention, the frontal portion includes an interior portion with an opening to slidably receive a corresponding portion of the rear portion. In another aspect of the invention, an interposer is positioned between the frontal portion and the rear portion to electrically couple the spaced apart connective interfaces. In still another aspect of the invention, the frontal and rear portions are axisymmetrically-shaped and have corresponding threaded portions to couple the frontal and rear portions.